Lubricating fluid

ABSTRACT

The object of the present invention is to provide a water-base lubricating fluid or a water-base hydraulic fluid in place of an oily liquid which has been used as a lubricating oil or a hydraulic oil applied onto the operating part of a machine and a device. The lubricating fluid of the present invention comprises fluoride ion, hydrogencarbonate ion, and water-soluble alcohols or their derivatives.

This application is a 371 of PCT/JP00/00780 Feb. 10, 2000.

FIELD OF THE INVENTION

The present invention relates to a novel lubricating fluid which maysupersede a lubricating oil used for a machine and a device or ahydraulic oil used for a cylinder, or the like.

BACKGROUND OF THE INVENTION

A lubricating oil is sent into a rotation part or a slide part of amachine or a device by a pump and the like, and prevents a sliding partfrom being burnt while reducing resistance caused by a rotation and aslide. In ordinary cases, when a machine or a device, for example, amachine tool such as a lathe, a milling cutter or a machining center orthe like, is used for cutting or grinding a workpiece, a cutting oil orthe like is flowed down over the part to be machined for variouspurposes. The spread cutting oil splashes on a bearing and a slide partof a bed, which results in mixing the lubricating oil and the cuttingoil. Therefore, lubricating oils are retrieved as part of cutting oilsand recycled while the lubricating oils are newly refilled.

Since waste oil problems are raised when these oils are disposed, and avolatile and transpiratory gas emitted from the cutting oils has therisk of impairing the health of workers as well as deterioration ofworking environment, water-base cutting fluids are expected and variouskinds of water-base cutting fluids have been proposed. However, when awater-base cutting fluid is used, for example, in a machine tool, thelubricating oil used in the machine tool flowing into the cutting fluidmakes an oil film appear on the surface of the cutting fluid and leadsto the solidification of the lubricating oil. Consequently, the machineitself has the risk of being adversely affected because the cuttingfluid is circulated in the machine. Further, when the cutting fluid isdisposed, it is necessary to separate the lubricating oil from thecutting fluid. The task is difficult, so that it has cost higher thanone using a cutting oil.

The use of a water-base lubricating fluid with a correspondingwater-base cutting fluid, therefore, causes no problems, even if thelubricating fluid has been mixed with the cutting fluid. In addition,any problems, such as separation of oil and water, or the like are notraised when the waste liquid is disposed. However, there have been nowater-base lubricating fluids, because when a water-base lubricatingfluid is used in a machine tool such as an expensive machining centerand the like, there are not only problems with rust, but also the riskthat a lot of resistance may be applied onto a high-speed rotatingdriving part and a heavily loaded base part in the process of cutting,which leads to the risk of seizure.

Furthermore, hydraulic oils used for operating devices, such ascylinders, or the like are conventionally oily. Describing this byexemplifying a cylinder used for a bulldozer, or the like, for example,it is important not only to operate a piston by supplying oil for acylinder, but also to prevent the cylinder from seizure, even when aheavy load is applied. For this reason, there has been no choice but touse oil-base hydraulic oils. Although water is used as a hydraulic fluidin the field of press working and the like, there have not been suchtypes that are used by circulating a hydraulic fluid between the pressand the tank.

The object of the present invention is to provide a water-baselubricating fluid or a hydraulic fluid in place of an oil-base fluidwhich has been used as a lubricating oil or a hydraulic oil applied ontothe operating portion of a machine and a device.

As the result of repeated studies to develop an excellent lubricatingfluid having high lubricating effects without any problems with itswaste fluid disposal, the inventors of the present invention haveattained the present invention.

DISCLOSURE OF THE INVENTION

It is the main point of a lubricating fluid according to the presentinvention to comprise fluoride ion; hydrogencarbonate ion; andwater-soluble alcohols or their derivatives. The term “lubricatingfluid” as used herein means a hydraulic fluid and the like used foroperating a driving device such as a cylinder, or the like as well as alubricating fluid used for lubricating a sliding part of a machineelement.

In such lubricating fluid, the above-mentioned water-soluble alcohols ortheir derivatives may be glycerin or ethylene glycol.

Such lubricating fluid further contains a rust inhibitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment of a lubricating fluid according to the present inventionwill now be described in detail. First, the lubricating fluid accordingto the present invention comprises fluoride ion; hydrogencarbonate ion;and water-soluble alcohols or their derivatives.

The essential components contained in the lubricating fluid of thepresent invention are fluoride ion; hydrogencarbonate ion; andwater-soluble alcohols or their derivatives. The concentration offluoride ion and hydrogencarbonate ion is not particularly limited, butthe lubricating fluid preferably contains within the range of 1×10⁻³ to10% by weight of fluoride ion, and within the range of 1×10⁻² to 10% byweight of hydrogencarbonate ion. Of the water-soluble alcohols or theirderivatives, glycerin, ethyl alcohol, methyl alcohol, and ethyleneglycol or their derivatives, or the like are preferable. Among them,glycerin or ethylene glycol or its derivative is particularlypreferable. The concentration of glycerin and ethylene glycol or itsderivative included in the lubricating fluid is not particularlylimited, but it is preferably within the range of 1 to 70% by weight,more preferably within the range of 2 to 60% by weight.

Accordingly, the lubricating fluid of the present invention can beprepared by dissolving, for example, a predetermined amount of sodiumbicarbonate, sodium fluoride, and ethylene glycol in distilled water andservice water or mineral water or the like, but the manner is notlimited. Sodium ion may particularly be substituted by one of otheralkali metal ions or other cations.

The lubricating fluid of the present invention may be used alone, but itmay further include other additives. A typical example of otheradditives is a rust inhibitor. It is, however, not limited to a rustinhibitor, but a suitable amount of thickener, leveling agent, colorant,and perfume may be added to the lubricating fluid in accordance with theactual service condition within the scope of keeping its performance.

The rust inhibitor used in the present invention may be any of rustinhibitors available in the market. For example, an ion coating rustinhibitor, a rust inhibitor including such as paraffin wax, carnaubawax, and the like, and a non-amine rust inhibitor, or the like arepreferably used. The rust inhibitor is added as necessary in someapplications to the lubricating fluid described in this patentapplication.

The lubricating fluid of the present invention can be obtained by mixingand/or dissolving fluoride ion, hydrogencarbonate ion, water-solublealcohols or their derivatives, and other arbitrary components into wateror other water-soluble solvent within the scope of the appropriateconcentration.

The present invention relates to a lubricating fluid including theabove-mentioned composition, wherein the surface of a steel product orthe like is protected by coating the product by fluoride ion,hydrogencarbonate ion and/or a water-soluble alcohol, moreover, thesliding resistance between members of the product is reduced by loweringthe friction factor. As a result, when the members are slid each other,there is no possibility of their contact surfaces seizing, even if thepressure applied onto the surfaces between both members gets higher dueto heavy load.

Further, for example, when the lubricating fluid is used in a machinetool as the water-base cutting fluid, the lubricating fluid and thecutting fluid are not separated, even if they have been mixed becausethis lubricating fluid is water-base. Especially, the lubricating fluidof the present invention has no risk of river contamination caused byspecial liquid waste disposal because it comprises of inorganiccomponents existing in nature.

The lubricating fluid according to the present invention may also beused on any place where either of an axial load or a thrust load isapplied. Consequently, the lubricating fluid can be used not only as alubricating fluid for a wide variety of machine tools, but also as alubricating fluid in sequential feeding system using a pump or the like.

Furthermore, the lubricating fluid according to the present inventioncan be used as a hydraulic fluid in place of a conventional hydraulicoil or hydraulic water for an oil hydraulic cylinder and a hydrauliccylinder. Particularly, the lubricating fluid of the present inventionis the most suited to be used as a hydraulic fluid for a cylinder onwhich a heavy load is applied, such as a power shovel or a bulldozer,because the lubricating fluid reduces frictional resistance. It isneedless to say that the lubricating fluid can be used as a hydraulicfluid for a hydraulic equipment.

The present invention will now be described in more detail by showingthe following examples. The present invention is, however, not limitedto these examples. The invention can be embodied by adding a variety ofimprovements, modifications, and changes, based on knowledges of thoseskilled in the art within a scope that does not depart from theessentials of the invention.

EXAMPLES Example 1

0.8 g of sodium fluoride (made by ARAKAWA CHEMICAL INDUSTRIES, LTD.),3.9 g of sodium hydrogencarbonate (made by WAKO PURE CHEMICALSINDUSTRIES, LTD.), 51 ml of ethylene glycol (made by ARAKAWA CHEMICALINDUSTRIES, LTD.; specific gravity 1.1155), 1929 ml of glycerin (made byARAKAWA CHEMICAL INDUSTRIES, LTD.), a 185 ml-rust inhibitor F2 (made byCHELEST CORPORATION), and a 1 ml-preservative (CHIYODA CHEMICAL CO.,LTD.) were dissolved in 1 L of distilled water to prepare a lubricatingfluid (3170 ml (1.169 g/ml)).

An endurance test on a machine tool was conducted by using thelubricating fluid of the present invention obtained in this manner.First, a lubricating oil was removed not only from the driving andsliding parts of a machining center (made by MORI SEIKI CO., LTD.,TV-400-497), and the lubricating oil tank. Then, a lubricating fluid ofthe present invention obtained instead of the lubricating oil wassupplied in a lubricating tank and the pump was driven so that thelubricating fluid may fully spread over each part, such as a bed. Afterthat, the machine sat no-load running to be confirmed each part movedsmoothly. Next, the following steps of machining from (1) to (5) wererepeated. Note that a water-base cutting fluid having a close componentstructure to that of the lubricating fluid of the present invention wasused.

(1) A plate material SS400 (300×100×30 mm) was mounted on the machine tocut its surface with a machining allowance of 0.5 mm and a finishingallowance of 0.2 mm using a face mill (made by SANDVIK, CoroMill 245,tool diameter 80.0 mm). More particularly, the roughing of the plate(depth of cut: 0.3 mm, width of cut: 60.0 mm, speed of rotation: 450rpm, and feed rate: 280 mm/min) was performed, a finishing was carriedout (depth of cut: 0.1 mm, width of cut: 60.0 mm, speed of rotation: 580rpm, and feed rate: 360 mm/min).

(2) A hole was drilled on the plate used in the step (1) to an effectivedepth of 10.0 mm. More particularly, a center drill (made by YAMAWA,CD-E 1.5×60°, tool diameter 1.5 mm) was used to drill a hole under theconditions of cycle: drill, speed of rotation: 2000 rpm, and feed rate:200 mm/min. Subsequently, the operation of drilling a hole with aprepared hole drill Wade by OSG, EX-SUS-GDS 2.6, tool diameter 2.5 mm)is repeated under the conditions of cycle: high speed depth, speed ofrotation: 3180 rpm, and feed rate: 320 mm/min until 189 pieces of holes,which were the total of 7×27, were drilled.

(3) The plate used in the step (2) was replaced with a plate materialAL5052 (300×100×30 mm), and then the surface of the plate was cut with amachining allowance of 0.2 mm and a finishing allowance of 0.2 m usingan end mill (made by OSG, V-XPM-EMS 20, tool diameter 20.0 mm). Moreparticularly, the roughing of the plate (depth of cut: 0.0 mm, width ofcut: 10.0 mm, speed of rotation: 1240 rpm, and feed rate: 350 mm/min)was performed, and then a finishing (depth of cut: 0.1 mm, width of cut:10.0 mm, speed of rotation: 1610 rpm, and feed rate: 450 mm/min) wascarried out.

(4) The plate used in the step (3) was replaced with a plate materialSUS304 (300×100×30 mm), and then the surface of the plate was cut usingan end mill (made by OSG, V-XPM-EMS 20, tool diameter 20.0 mm) with amachining allowance of 0.2 mm and a finishing allowance of 0.2 mm. Moreparticularly, the roughing of the plate (depth of cut: 0.0 mm, width ofcut 6.0 mm, speed of rotation: 300 rpm, and feed rate: 60 mm/min) wasperformed, and then a finishing (depth of cut: 0.1 mm, width of cut: 6.0mm, speed of rotation: 390 rpm, and feed rate: 80 mm/min) was carriedout.

(5) After a prepared hole was drilled on the plate used in the step(4)to an effective depth of 7.0 mm, chamfering was accomplished (type:Metric, width of chamfer: 0.3 mm). And then, an internal thread (nominaldiameter: 3.0 mm, pitch: 0.5 mm) was cut on the hole. More particularly,a hole was drilled with a center drill (made by YAMAWA, CD-E 1.5×60°,tool diameter 1.5 mm) under the conditions of cycle: drill, speed ofrotation: 1400 rpm, feed rate: 160 mm/min, and then a hole was drilledon the hole with a prepared hole drill (made by OSG, EX-SUS-GDS 2.6,tool diameter 2.5 mm) under the conditions of cycle: deep hole, speed ofrotation: 1910 rpm, and feed rate: 130 mm/min. After that, chamferingwas accomplished with a chamfering drill (made by OSG, TIN-NC-LDS 6×90°)under the conditions of cycle: drill D, speed of rotation: 2670 rpm, andfeed rate: 160 mm/min. Next, an internal thread was cut on the hole witha tap (made by OSG, EX-SUS-SFT m3×0.5, tool diameter: 3.0 mm) under theconditions of cycle: synchronous stop, speed of rotation: 1170 rpm, andfeed rate: 0.5 mm/min. The above-mentioned step was repeated until thetotal of 189 pieces of internal threads summing up 7×27 were formed.

The above-mentioned steps from (1) to (5) were repeated. And inspectionsas necessary for abnormalities on each part of the machining center weremade when a machine is stopped to be exchanged workpieces. As a result,no abnormalities occurred in an operation test for the total number of800 hours (results obtained by the day before the patent application).Although the lubricating fluid was refilled during the period of theoperation test, no abnormalities were encountered in the machiningcenter as well as in both tanks for the lubricating fluid and thecutting fluid.

Example 2

With the use of a centrifugal pump (made by NISHIJIMA SEISAKUSHO,EC40=28), the above obtained lubricating fluid was charged onto thebearing part of the pump. A day and night continuous operation test wasperformed for the total number of 2472 hours (results obtained by theday before the patent application). However, no abnormalities wereencountered because the situation was completely same at thecommencement of operation through the operation test.

Example 3

With the use of a mini-power shovel (made by KOMATSU LTD. on Dec. 15,1985, PC-20, type 5), the above obtained lubricating fluid was chargedinstead of the hydraulic oil supplied with cylinders for the powershovel and change-direction. No abnormalities were encountered becausethe situation was completely same as the time of commencement, evenafter an operation test of movement with a travel and a turn between theparking place and the workplace, as well as hole digging for the totalnumber of 505 hours (results obtained by the day before the patentapplication). In addition, no abnormalities were encountered, even whenthe power shovel was operated by immediately starting of an engine andchange-direction after leaving the power shovel under the environment atan outside air temperature below −6° C. for more than 10 hours duringthe period of this operation test.

INDUSTRIAL APPLICABILITY

As described above, the lubricating fluid of the present invention hasno risk of seizing up of components because of its high lubricatingeffects and low viscosity which reduce the frictional slidingresistance.

Since the lubricating fluid of the present invention does not containany components which emit an offensive odor as volatile andtranspiratory compositions, and contaminate the environment, the fluidis easy to use and environmentally friendly. Further, no specialwastewater treatment is required for the lubricating fluid, even whenthe fluid is disposed as a waste fluid because it does not contain anymaterials adversely affecting the environment. Further, the lubricatingfluid of the present invention can be used together with a water-basecutting fluid because of its water-base characteristics so that both ofthe effects of the lubricating fluid and the cutting fluidsynergistically contribute to workability and environmentalfriendliness.

What is claimed is:
 1. A lubricating fluid comprising: water; fluorideion; hydrogencarbonate ion; and water-soluble alcohols or theirderivatives.
 2. The lubricating fluid according to claim 1, wherein saidwater-soluble alcohols or said derivatives are glycerin or ethyleneglycol.
 3. The lubricating fluid according to claim 1, which furthercontains a rust inhibitor.
 4. The lubricating fluid according to claim2, which further contains a rust inhibitor.